(i) Field of the Invention
The present invention relates to the addition of phosphines to alpha-olefins, and related processes using phosphine oxides and phosphine sulfides. More particularly, the invention relates to the preparation of alkyldiphenylphosphines by a simple thermal reaction at elevated temperatures without the use of an initiator.
(ii) Prior Art
The addition reaction of alpha-olefins with phosphines is extremely well known in the art. For example, see Organic Reactions, edited by R. Adams et al., at Vol. 13, pgs. 218-214; Methoden der Organischen Chemie by Houben-Weyl, Vol. 1, pgs. 113-119; and Organic Phosphorus Compounds by Kosolapoff and Maier at Vol. 1, pgs. 61-68.
In general, the reaction of alpha-olefins with phosphines is normally catalyzed with bases, acids, free radical initiators, or radiation. Thermal reactions of phosphines and alpha-olefins have been noted with a few specific haloolefins without added catalysts. For example, Organic Reactions states " . . . phosphine has been added to several fluoroolefins at 150.degree. C. without added catalysts. From tetrafluoroethylene a mono- and a di-adduct are obtained in addition to tetrafluoroethylene diphosphine. It is not clear whether or not these are free radical reactions." A review of the footnoted reference indicated that many other haloolefins failed to react under the same conditions. Likewise, it should be noted that Houben-Weyl has a "blank" under the catalyst column, at page 117, Table, row 1. This appears to be a typographical error since the footnoted reference apparently used a peroxide-type catalyst.
A computer search of Chemical Abstracts over the period 1967 to present, turned up only three references directed to n-hexyldiphenylphosphine and having the corresponding CA code number "RN-18298-00-5". None of these references relate to processes for preparing phosphines (or related products such as arsines), but rather to their properties and utility, as summarized below.
U.S. Pat. No. 3,322,542 (Ullmann et al) is entitled "Stabilization Additives for Photochromic Compounds". Its Example 49 relates to the use of "diphenylhexylphosphine" (DPHP) as such an additive, and a number of the other examples relate to the use of other phosphines.
"Allylic Alkylations Catalyzed by Nickel" by Cuvigny et al. in J. Organomet. Chem., 250(1), C21-C24, apparently also refers to the use of hexyldiphenylphosphine as a catalyst for allylic alkylation of enolates.
"Carbon-13 NMR Spectra of Tertiary Phosphines, Arsines, and their Onium Salts" by Koketsu in Physical Organic Chemistry, Vol. 12, at pages 1836-43 reports the 13C-NMR spectra for compounds containing a phosphorus or arsenic atom, including alkyldiphenylphosphines such as hexyldiphenylphosphine.
"The Preparation and Reactions of Diphenylphosphinous Chloride" by C. Stuebe et al. in J. of the Amer. Chem. Soc., Vol. 77, pgs. 3526-3529 (1955) includes a method of preparing hexyldiphenylphosphine at pgs. 3527-3528. It points out that diphenylphosphinous chloride reacts readily with Grignard reagents to give tertiary phosphines in good yield. From FIG. 1, a "good yield" appears to be 70-75%. It is believed that this reaction would not be easy to run on a plant scale.
"The Free Radical Addition of Phospines to Unsaturated Compounds" by M. M. Rauhut in The Journal of Organic Chemistry, Vol. 26, pages 5138-5143 (1961) describes the preparation of octyldiphenylphosphine by the free radical initiated addition of diphenylphosphine to 1-octene, and other related compounds. This reaction is generally low yielding and difficult to carry to completion.
Essentially, nowhere does the vast prior art appear to report an uncatalysed thermal reaction with unactivated double bonds.